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Airfix Short Sunderland to Empire


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On 12/11/2019 at 15:20, DMC said:

Car wash size?

A3 (the paper size, not an Audi). The plastic card is also A3 (297x420mm) and a sheet of B&Q plywood is 600mm wide. So by the time I've cut it in half and planed off a bit for my wobbly saw cuts, pretty much bang on.

 

On 12/11/2019 at 15:24, Courageous said:

How did you get your wobbly plastic past those corners?

The plastic is stapled/taped to the "front" of a rectangular frame made out of 46x10mm wood. The corners are glued into the "back" of the frame for strength because I didn't want it to turn into a parallelogram when grabbing it out of the grill. So it is all managed with no inter-dimensional nuclear interference!

 

Regards,

Adrian

 

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Great achievement! I admire your efforts and skills.  How you have heated plastic? Is it a bit soft when you start pumping?  Or you first pump and them start to heat?  It should be heated in an uniform way, Maybe it is kind of experience you have to get. The size of model is not helping here. 

Regarding a bit waving surface - It can be due to not perfect evacuation of air from surface of your "stamp" or form (so between plastic and form). All vacu kits I had in my hands have small dots seldomly on surface, which are the sites of air evacuation holes, which are present on the form at distance of some cm apart one from another. You did air evacuation matrix on sides but you have not drilled your fuselage (stamp/form) in any place. So when the plastic wraps around it if an air bulb will be trapped it cannot be evacuated.

I do not have any personal exparience with vacu, only my experimantal physicist background tells me that... So maybe I am wrong  :)

Cheers

J-W

 

Edited by JWM
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3 hours ago, JWM said:

How you have heated plastic

I put it under the grill of my domestic oven. Possibly it gets warmer in the middle than the edges. I should maybe try oven not grill next time. The plastic is heated and floppy when I bring it to the mould.

 

It’s my first try at anything bigger than a canopy so I’m quite heartened to get anything at all. Adding more vent holes might help, but I’m also working on the pattern to make it better:

471-E7-AC9-1-F68-4-FFD-9-D58-8-F3-D43-BC

 

The first attempt does sorta come together in an empire shape, but I know I can do better...

 

Regards,

Adrian

 

 

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6 hours ago, AdrianMF said:

I put it under the grill of my domestic oven. Possibly it gets warmer in the middle than the edges. I should maybe try oven not grill next time. The plastic is heated and floppy when I bring it to the mould.

 

It’s my first try at anything bigger than a canopy so I’m quite heartened to get anything at all. Adding more vent holes might help, but I’m also working on the pattern to make it better:

471-E7-AC9-1-F68-4-FFD-9-D58-8-F3-D43-BC

 

The first attempt does sorta come together in an empire shape, but I know I can do better...

 

Regards,

Adrian

 

 

I would be over the moon at that as a first go, but I know what you mean when you know you can improve it. Good luck with the work

 

Rob

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Did you use any mold release wax? If not, that might help with the separation damage issue. Also, the reinforcement you have added underneath the halves might benefit from a bit more. I've not done much vac form work and I don't know how powerful your air source is but I wouldn't like to see the masters cracked by the vacuum if they flexed.

 

Alec Tirranti (?) in London is a good source for most moulding supplies.

 

I can appreciate more the work of Gordon Stevens, with his Rareplane range, when I see the amount of work you are putting in here.

 

First class work so far and thanks for sharing it with us.

 

Tony.

Edited by TonyW
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Having made a late start in this GB I'm on catch-up. Just read through your thread Adrian, an incredible job!

 

And nice to see that I'm not the only one using P38 filler, a bit less in my case,

 

Best of luck for the rest of the project, will be following with interest.

 

Cheers,

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Any fatty stuff can also work for separation, applied thin I guess, Mybe best is mineral oil.  Wax is of course used widely in any metal casing, but i am not sure if applicable here - for sure one have to separate it some way from sucked air, so a kind of trap for wax is needed between pump and and form. In laboratory we are using this kind bottle as separtor :

images?q=tbn:ANd9GcTspyyBrOvNRXi-yuNS7eQ

 

The connection to form is on left side, the pump is on right, But here the free volume of flask below the end of tube should be big enough to trap all wax used, so the long pipe should be shortered. 

I will not suggest to use wax unless some experience vacu production experts will confirm it, lets try to ask @John Aero

Cheers

J-W

 

 

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I use cooking oil as a release agent for the small resin items I cast - works fine but of course you then have to wash it off before painting. For small parts I just put them in a jar of water with a denture cleaning tablet but with something this size I guess it could be a bit more of a problem.

 

Pete

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When doing the Russian method of male moulding vac forming (Sukova) rather than the Japanese female moulding method (Sukinto).  the best way to drag the hot plastic down (draping) over the former (model or pattern) is to have a lot of holes closely drilled around the periphery of the former. also warm the former as much as you can.

Also drill some strategic holes through the former it'self, such as at the point on the fuselage where the hard chine of the hull has a trough or dimple  

The vacuum in a simple setup is not very high, so when the heated sheet touches the surface between evacuation holes it seals the area and if there is a hollow in the former surface there is not enough vacuum for the external air pressure to push the thickness of the plastic into the hollow.

 

When using the male moulding method don't put any detail on, however tempting such as the cockpit cutout. It will just leave an awkward rounded lip on the edges of any recess when it's cut out. Just light score lines on the former are sufficient as these will show on the inside of the moulding, so you still have a guide to cut the part out. If you have made your pattern to have an accurate centre line then mount your formers on a plinth of thin (1.5 mm) sheet cut tightly to the profile. This extra height will take care of the webbing curve at the base of the plastic moulding. This curved edge has to be cut off but the joining/ centre line of your plastic fuselage will be accurate and a much better fit. 

 

You can make a simple cutting tool by bonding a new Stanley blade onto a piece of 1 mm plasticard so that a corner of the blade pokes over the edge, then bond another thicker piece of card on top to act as a handle. Place this tool flat on the backing sheet of the moulding you wish to remove and slide it around the fuselage part so that the exposed blade scores the fuselage halves all the way round. The blade 'V'edge mounted on the 1 mm base is then roughly 1.5 mm high from the backing sheet so it allows the waste backing material to then be broken away, like a normal vacform.

 

If you are moulding over a deep narrow object then you may encounter webbing or creases at the corners. if this happens then build a Plasticine dyke or moat around the model about 15 mm away from the former and 15 mm high. If it's something like an engine cowl then the dyke can be smaller

For the Former/pattern, use fine grained timber.  English Lime or American Bass wood are among the best. Balsa is not good. Miliput is very good and  P.38 type fillers are fine up to a reasonable temperature.  Styrene distorts at around 70 deg C

 

Mould release 'wax in suspension' aerosols are readily available but DO NOT use one containing silicone. John Burn and Co, Alchemie, Tiranti and MTT all sell them. The smoother the surface the easier the moulded plastic will come off.

 

Send for the Tiranti catalogue or look up mould making supplies.


 

Health warning - Sukova and Sukinto are my own humorous vacforming  terms and may be lost in translation.

 

John

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Useful info John, as is your input on the erroneously long nose on the Matchbox Meteor NF 14 I am building on another GB, and as quoted in the 2006 Aerofax book on the subject.

 

Cheers

 

Pete

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I forgot to add, this is an excellent project, which I looked in on rather late, and really well executed.

 

The plans of Mia and Mercury shown in an earlier post have the distinct look of being part of the Harleyford (ex Aeromodeller) collection . Many of these 1/72 scale drawings were prepared to be part of an ambitious series of books on British aircraft manufacturers, of which only three were published. The three were Miles, Westland and Bristol. Later in the 1950's the large number of 1/72 drawings were made available as Plan Packs or loose drawings. I have the three books and quite a number of the drawings (but not the Mia and Mercury).

 

It would have been an amazing reference library had they been completed. Some of the drawings are not the most accurate by today's standards but many are very useful even now. The drawing 'families' are Vickers, Hawker, Miles, Bristol, De Havilland, Westland and Fairey, with probably a few more.

 

John

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Just a word of warning to anyone wanting to make a home made vacformer. You need a good distance initially between the plastic and the model while it's being heated. Heat will quickly pass through the plastic sheet and damage the pattern.

 

In most commercial vacform machines there is a retractable drape table on which the pattern is placed. The plastic sheet is clamped in a frame about 150 mm/6" above the retracted table. The heater is on and pulled to one side on rails. The heater is drawn over the plastic and when this is hot enough ( with timers) the drape table is raised up to the plastic clamp frame thus sealing it and the vacuum is switched on, drawing the hot plastic onto the mould. The heater is immediately retracted so it cannot transfer direct heat through to the pattern or mould.

 

If you want to make an epoxy female mould then the release agent I always used on my patterns is a Blue liquid PVA. It is applied with a soft brush and it drys quickly leaving a microns thick membrane over the pattern. It's easily removed by washing the mould and pattern in cold water. For the female mould vents I don't drill the vent holes, I use my own preformed vent hole formers. The cost of a female mould (materials only) for one suitable for the C Class would be in the region of £100 and it would not work with a low vacuum..

 

John

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